TURQUul^ STOFE. 18§ 



fectly similar to those in the Cabinet of Maseam of ^'''ah-.ral 

 History; and M. Hauy, whom I consulted, could nut auirm 

 whether they were truly from Prussia. M.Gujton thinks that 

 there is a difference between the turquoises of Persia and the 

 Occidental. 



This philosopher has announced, for several years, in his 

 course of mineralogy, at the Polytechnic School, that the former 

 contained silex. It is possible that turquoises may >contain 

 this earth accidentally ; but 1 have not found it in any of those 

 which I examined. This difference ought not, I think, to 

 suspend the classification of this substance by mineralogists. 

 M. Guyf on himself has already placed it among fossil bones. 

 This celebrated chemist has likewise made some comparative 

 experiments. He has found that fossil bones assume, in th^ 

 fire, a colour similar to that of turquoises ; that, when digested 

 in wafer containing pot-ash, they turn blue; and that this 

 blue varies in its shade, by passing from greenish blue to deep 

 blue; and, lastly, that bones, exposed lo the air, become 

 white. 



Messrs. Fourcroy and Vauquelln have likewise observed, 

 that bones, strongly calcined, often assume a bluish tinge : 

 this colour appeared to them to be owing to the presence of a 

 small quantity of phosphate of iron. 



There cannot, therefore, any longer exist a doubt respecting ObserTatlon 

 the matter which colours the turquoises. If it were necessary ^"'^ experi- 

 to add any thing more to the facts announced, I should observe, ^^ ^ colouring 

 that having put the same turquoises which I analyzed, into the matier. 

 hands of Mr. Vauquslin, he did not find a particle of copper 

 in them ; and, lastly, I have ascertained that, by pouring into 

 a solution of muriate of lime, phosphate of soda and some 

 drops of muriate of iron at the maximum, the phosphate of 

 lime and of iron is obtained, of which the colour is a greenish 

 blue. We may, likewise, by decomposing the phosphate of / 



soda by muriate of iron at the maximum, obtain a phosphate 

 of iron, which is not white, as some chemists have asserted, but 

 ofagr6en bluish colour. 



These reflections, without doubt, are not very important; 

 but I present them as tending to show the possibility of imi- 

 tating the colour of the turquois, and at the same time to 

 show that iron can, in various circvmistances, afford colours 

 .similar to those of copper. 



Vil. 



